The City was aware contractors planned to purchase what officials now say was the wrong type of steel for the Central Subway’s tracks as far back as 2015, new documents obtained by the San Francisco Examiner suggest.

The revelation comes after transportation officials called for construction contractors to pull those tracks out and replace them, alleging the contractors purchased and installed the wrong type of steel. Emails obtained by the Examiner, however, show the San Francisco Municipal Transportation Agency had knowledge that the steel was ordered by contractors three years ago.

City officials have said the $1.6 billion Central Subway project, which stretches from South of Market to Chinatown, could be delayed at least another month because contractor Tutor Perini and its subcontractor, Con-Quest Contractors, inc., laid 3.2 miles worth of “standard” strength steel. The SFMTA said the project instead called for “high” strength steel, according to an email.

Tutor Perini and Con-Quest Contractors Inc. have denied The City’s claims and said it could cost $2.6 million to replace the tracks.